This study aims to ascertain the relationship between inventory management and operational performance of quoted manufacturing firms in the south-east; one of the geographic regions with high industrialization prospects in Nigeria. To achieve this, operational performance of manufacturing firms and their association with components of inventory management; inventory cost, just-in-time approach, materials requirement planning and strategic supplier partnership, was examined through a questionnaire. Three hundred and seventy-one copies of a questionnaire issued to five hundred and thirty-eight sampled respondents of four quoted manufacturing firms in the south-east region of Nigeria were properly filled and found relevant to the study. The study used SPSS and Excel-based descriptive statistics to analyze the data collected. Regression analysis was used to test the hypotheses of the study. Study results conclude that there is a positive significant relationship between; inventory cost, just in time approach, materials requirement planning and strategic supplier partnership and operational performance of quoted manufacturing firms in the south-east region, Nigeria. The study recommends among others that, manufacturing firms in south-east Nigeria should adopt inventory practices such as strategic supplier partnership, just-in-time approach, materials requirement planning and inventory cost control due to the significant effect these practices have on operational performance.